/usr/share/xul-ext/imap-acl/chrome.manifest is in xul-ext-imap-acl 0.2.6-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | content     imapaclext    										    	chrome/content/
overlay		chrome://messenger/content/mailWindowOverlay.xul	chrome://imapaclext/content/overlay.xul
skin		imapaclext   				classic	   				    	chrome/skin/
style		chrome://global/content/customizeToolbar.xul		chrome://imapaclext/skin/overlay.css
locale 	    imapaclext   				en-US	   				     	chrome/locale/en-US/
locale 	    imapaclext   				de-DE	   				     	chrome/locale/de-DE/
locale 	    imapaclext   				fr-FR	   				     	chrome/locale/fr-FR/
locale 	    imapaclext   				pt-BR	   				     	chrome/locale/pt-BR/
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